The present invention relates to a method of manufacturing a replica diffraction grating which is used in a spectrophotometer or the like.
Conventionally, when a large number of diffraction gratings are produced, a replica diffraction grating is produced from a master diffraction grating. Such a method will be explained with reference to Patent Documents 1 and 2.
First, a thin film of metal such as aluminum is deposited on a surface of a glass substrate, and grating slits are etched in the thin film to form a master diffraction grating. With the master diffraction grating as a parent mold, silicone grease is thinly coated on a grating surface as a release agent to form an oil film, and a thin film of metal such as aluminum is formed on the oil film with vacuum vapor deposition. A glass substrate (replica substrate) is adhered to the metal thin film via an adhesive such as an epoxy resin, and the replica substrate is removed from the parent mold after curing the adhesive. Accordingly, the metal thin film having the grating slits is transferred to the replica substrate in a reverse form, and the replica diffraction grating is completed.
In the method described above, the release agent is used so that the replica substrate is easily removed from the parent mold. A film layer of the release agent is present between the grating surface of the master diffraction grating and the metal thin film serving as the replica diffraction grating surface. Accordingly, if the film layer is not uniform, the releasing property becomes poor. If the releasing property is degraded, it is difficult to transfer the grating surface from the master diffraction grating to the replica diffraction grating. In particular, when fine size grating slits called nano-imprint are transferred, degradation of the releasing property tends to be linked to lowering precision of the grating surface. Accordingly, it is difficult to obtain a wavelength scattering-characteristic of the replica diffraction grating as designed.
Patent Document 1: Japanese Patent Publication (Kokai) No. 07-146405
Patent Document 2: Japanese Patent Publication (Kokai) No. 07-261010
In view of the problems described above, an object of the present invention is to provide a method of manufacturing a replica diffraction grating in which a grating surface of a master diffraction grating can be transferred to a grating surface of a replica diffraction grating with good precision.
Further objects and advantages of the invention will be apparent from the following description of the invention.